Temperature responsive slip friction switch



1966 s. c. BIXBY ETAL TEMPERATURE RESPONSIVE SLIP FRICTION SWITCH Filed Aug. 13, 1963 u, E 9. m R m; m Nu r 5 n V./. m x E. Z 5/ w United States Patent 3,235,631 TEMPERATURE RESPONSIVE SLIP FRKCTEQN SWlTCH Stephen C. Bixby, Rolling Hills, and Eric P. Selinder, Palos Verdes Estates, Calif, assignors t0 Honeywell Inc., a corporation of Delaware Filed Aug. 13, 1963, Ser. No. 301,830 6 Claims. (Cl. 200-137) This invention relates to a thermostatic control device, and more particularly to a device to be mounted on the stack of a furnace to sense the heat therein which would indicate the presence of a flame. Devices of this type are well known in the heat controls art and are of various constructions. This particular control embodies a slip friction mechanism which causes the flame sensing portion thereof to quickly actuate a set of contacts upon initial movement thereof upon both a rise in temperature as well as a drop in temperature, providing for additional movement of the flame sensing unit beyond a contact making position and a contact breaking position which provides for only a slight spacing of a movable contact from a fixed contact. The device also includes a specific and novel calibrating and mounting unit for the flame sensing portion thereof in the units housing.

The industry is constantly endeavoring to improve the quality of flame sensors of the above-mentioned type as well as to make them more compact and reduce the cost thereof.

One of the objects of this invention is to provide a flame sensor type of control device which is inexpensive in construction, yet reliable in operation and easy to service in the field.

Another object of the invention is to provide a control device with an improved slip friction construction between the thermostatic actuator and the switch actuated thereby.

A' further object of the invention is to provide a flame sensing unit which is easy to manufacture and assemble.

A further object of the invention is to provide in a slip friction switch actuator, a movable contact blade or arm construction wherein a portion of the blade serves as as'pring to bias a slip friction member against its actuating rod.

Still further objects of the invention will become apparent upon reading the following detailed description of the invention in conjunction with the accompanying drawing wherein:

' FIGURE 1 is a vertical sectional view through the control device;

FIGURE 2 is a cross-sectional view taken along line 2- 2 of FIGURE 1;

FIGURE 3.is a fragmentary cross-sectional view of the invention taken along line 33 of FIGURE 2; and,

FIGURE 4 is a perspective view of the movable contact arm and the slip friction means associated therewith.

The body or housing of the control device is generally designated by the reference numeral 11 and consists of a body 12, preferably made of electrically insulating material (such as a ceramic), having a cavity 13 in one side thereof and a stepped bore 14 extending from the cavity 13 axially through a wall thereof. Extending through the wall in space relationship with respect to the stepped bore 14 is a terminal member 15 which is riveted at 16 to a plate 17. The plate 17 carries a fixed contact 18 at the outer end thereof. A second terminal member 19 extends through the side wall, on the opposite side of the stepped bore from the terminal member 15 and is riveted at 20 to a bracket or cage 21. The other end of the bracket 21 is secured to the wall by means of a bolt 22 extending through the wall and through a threaded opening in the bracket.

Secured to the bracket 21 by the rivet 20 is a movable contact arm 23 which has a stepped slot 24 extending axially thereof and two apertures 25 and 26, the first of which receives the rivet 20 and the second of which receives a second contact 27 which cooperates with the contact 18. The stepped slot 24 has a reduced width portion 24a in which is mounted a pair of half cylinders 28a and 2819. Each of the half cylinders have a kerf or slot 29a and 2% at each end of the arcuate portions thereof which fit above and below the side walls of the slot portion 24a. The half cylinder 28a also has a kerf or slot 30a which lies above and below the end of the slot 24a to prevent rotation of the half cylinder 28a in the slot. The half cylinder 28b likewise has a kerf slot 30b which receives the end of an arcuate finger 31 formed from the contact arm 23 and extending from the end of the wide portion of the slot 24 into engagement with the half cylinder 28b to resiliently bias it towards the half cylinder 28a. The half cylinders thus frictionally engage an actuator rod 32 that extends completely therethrough.

and through apertures in the bracket or cage 21.

The bracket 21 has an L-shaped portion 21a that extends around the slip friction half cylinders and carries at the lower end thereof an adjusting screw 33 which bears at its inner end against a portion of the bracket 21 adjacent the rivet 20 to vary the space bet-ween it and the portion of the bracket secured to the wall of the casting 12. A slot 34 provides for the extension of the contact arm 23 from the half cylinders to the fixed contact 18. A generally V-shaped rib 35 is formed in the L-shaped portion to make it rigid.

The-actuating rod carries an abutment washer 36 thereon in an annular groove and is spring biased outwardly of the cavity 13 by means of a coil compression spring 37 positioned in the stepped bore and bearing against the abutment washer 36. 1

A flame sensor in the form of a rod and tube actuatorgenerally designated by reference numeral 38 consists of a metal tube 39 and an invar or ceramic rod 40 positioned therein. One end of the tube 39 is spot welded at 41 to a plug 42 whch is suitably secured to one end of the rod 40. The other end of the rod 40 has a conical recess 40a therein which receives the cone-shaped adjacent end of the rod 32. The compression spring 37 normally holds the rod 32 against the rod 43 so as to cause the actuating rod 32 to follow the movement of the free end of the rod 40. The other end of the tube 39 has a radially outwardly extending flange 39a that extends into an internal groove 43a of an externally threaded sleeve 43. The sleeve 43 is threaded into an internally threaded nipple 44 which, in turn, has a reduced diameter portion 44a that extends through an opening in a cap or cover 45. The nipple is secured in the cover 45 by staking as at 44b. The cover 45 is secured over the cavity 13 and around the casting 12 by having the peripheral edge 35:: thereof rolled over a shoulder portion 12a of the body 12. The nipple is externally threaded at 440 to receive a clamp nut 46 which isadapted to clamp the wall of a furnace stack (not shown) against a shoulder 44d of the nipple, in a conventional manner.

To provide for manually moving the half cylinders 28a and 28b in a contact making direction, a forked lever 47 is pivoted intermediate its ends in a slot formed in the bracket 21 with a fork of the lever straddling the actuating rod 32 between the portion 21a of the bracket and the adjacent ends of the half cylinders 28a and 28b. An arcuate leaf spring 48 has reduced width portions 48a extending through a slot 21b in the bracket 21 and a slot 47a in the lever 47 to normally bias the lever 47 in a clockwise direction to hold the forked end thereof against the portion 21a of the bracket and in space relationship with respect to the half cylinders. This lever 47 serves as a stop for the half cylinders as they move to the left as viewed in FIGURE 1 of the drawing. A manually operable plunger 49 extends through a stepped bore 59 in the wall of the casting 12 and terminates a short distance from the lever 47 in its normal position with the forked end against the bracket portion 210. This plunger is movable inwardly to move the lever in a counterclockwise direction to move the half cylinders to the right as viewed in FIGURE 1 of the drawing, the spring 37 being sufficiently strong to hold the actuating rod 32 against the frictional forces exerted by the half cylinders on the rod 32 doing this movement.

While no second fixed contact is illustrated in the drawing, it is to be understood that such a fixed contact could be positioned on the other side of the lever 23 from the contact 18 and in space relationship therewith, so as to enable the movable contact arm 23 to complete a second circuit therethrough as the contact arm 23 moves away from contact 18 and into engagement with the second fixed contact. The body 12 is-provided with openings 51 and 52 to enable the addition of connectors similar to those shown at and 19 if such an additional function of controlling a second circuit is desired.

Operation The control device is illustrated as being in the condition that the components thereof would. assume if the control device were installed in a chimney duct of a heating installation and there is no flame present. This means that the tube 39 is at its normal unheated condition causing it to be of its shortest length and holding the rod as far to the right as it normally goes under this condition. In this condition, the half cylinders are held against the right-hand portion of the bracket 21 with the contact 27 in engagement with the contact 18, assuming that the connectors 15 and 19 are connected in a circuit to an igniter for the burner installation for which the control is mounted. It is possible for the burner to be ignited provided other controls therein in the circuit call for such action. If this ignition should take place, the tube 39 would quickly respond to heat generated in the furnace and cause the rod 40 to try to pull away from the actuating rod 32 and thus permit the compression spring 37 to cause the rod 32 to move to the left, as viewed in FIG- URE l, carrying with it the half cylinders 28a and 28b. This movement of the half cylinders would cause the contact arm 23 to move contact 27 away from contact 18 and against the abutment lever 47 to break the igniter circuit. Any additional movement of the rod 32 would result in the rod 32 slipping between the two half cylinders, the bias of the spring finger 31 being insufficient to prevent this movement under the bias of spring 37.

The elements will stay in the newly assumed position until the burner of the furnace is shut off, thus permitting the temperature in the stack to reduce and cause a reverse action of the rod 40 to quickly cause closing of the contact 27 against contact 18 to condition the ignitor circuit for re-ignition of the burner upon such a demand. Here again, the initial movement of the rod 40 to the right as viewed in FIGURE 1 will cause the contacts to close followed by a slipping movement of the rod 32 through the half cylinders to provide for any additional movement thereof by the flame sensing portion of the unit.

If it is desired to change the calibration of the flame sensor in the field, the position of the inner end of the sleeve 39 may be changed with respect to the casting 12 by screwing the sleeve 43 inwardly or outwardly of the nipple 44. This may be accomplished by inserting a spanner type of screwdriver into the slots 43b formed in the outer end of the member 43.

While the preferred construction of the invention has been described above, it is deemed to be obvious that modifications may be made within without departing from the spirit of the invention. Therefore, the scope of the invention should be determined by the appended claims.

We claim:

1. The combination comprising a bracket, a fixed contact in said bracket, a pair of slip friction connected elements consisting of a movable arm and an actuating rod, said movable arm having a fixed end operably secured to said bracket and having a free end movable with respect to said bracket, said arm having a transverse slot therein intermediate its ends, first and second channel-shaped members having a width greater than the width of said slot and having a transversely extending kerf in the sides of each, said members being located in said slot with the sides of said slot lying in said kerfs and one end thereof bearing against the first of said members, said arm having spring means extending from the other end of said slot to said second of said members to resiliently bias said second member towards said first member, said actuating rod extending slidably through and frictionally engaging said members and holding them apart against the bias of said spring means so that said rod and said channel-shaped members form a slip friction connection between said arm and said rod, a movable contact movable by a first of said two slip friction connected elements and cooperable with said fixed contact to perform a switching action, stop means positioned to limit the movement of said first of said elements in a direction generally along the axis of said rod but allowing suflicient movement thereof to operate said contacts, and condition responsive means operably connected to the other of said slip friction connected elements and operable in response to a change in condition to first move said two elements and said channel-shaped members as a unit to operate said contacts and thereafter to cause sliding relative movement between said rod and said members after the engagement of said first element with said stop means so that said other element moves with respect to said first element.

2. The combination defined in claim 1 wherein said spring means is in the form of a leaf spring.

3. A switch comprising a bracket, a fixed contact in said bracket, a movable contact arm secured at a first of its ends in said bracket at a point spaced from said fixed contact and having a free second end positioned adjacent to said fixed contact for cooperation therewith to perform a switching action, said arm having a transverse slot therein intermediate its ends, first and second half cylinders having an outside diameter greater than the width of said slot and having a non-round surface portion in the outer central surface of at least one of said half cylinders and a kerf in the side edges of each of the half cylinders, said half cylinders being located in said slot with the sides of said slot lying in said kerfs of each of said half cylinders and one end of the slot bearing against said flat surface portion of the first of said half cylinders, said arm having spring means extending axially within said slot from the other end of the slot to said second half cylinder to resiliently bias said second half cylinder towards said first half cylinder, an actuating rod for said arm extending slidably through said half cylinders and holding them apart against the bias of said spring means, stop means positioned to limit the axial movement of said half cylinders by said actuating rod at a position Where the contacts are closed or at a position where the contacts are spaced a short distance apart depending upon the direction of movement of said actuating rod, and means for actuating said rod to first move said half cylinders and contact arm and then to slide said rod between said half cylinders after said stop means has been engaged.

4. A switch as defined in claim 3 wherein said spring means is an arcuate finger formed out of the material of said contact arm.

5. A thermostatic device comprising a housing, a fixed contact in said housing, a movable contact arm secured at a first of its ends in said housing at a point spaced from said fixed contact and having a free second end positioned adjacent to said fixed contact for cooperation therewith to perform a switching action, said arm having a transverse slot therein intermediate its ends, first and second half cylinders having an outside diameter greater than the width of said slot and having a non-round surface portion in the side edges of each of the half cylinders, said half cylinders being located in said slot with the sides of said slot engaging said non-round surface portions and one end of the slot being in engagement with the first of said half cylinders, said arm having an arcuate finger extending axially within said slot from the other end thereof with the free end of the finger engaging the second of said half cylinders to resiliently bias said second half cylinder towards said first half cylinder, an actuating rod for said arm extending slidably through said half cylinders and holding them apart against the bias of said finger, temperature responsive means positioned to actuate said rod axially to operate said half cylinders and contact arm with respect to said fixed contact, and stop means positioned to limit the axial movement of said half cylinders by said actuating rod but permitting continued movement of said rod between said half cylinders.

6. A thermostatic device comprising a housing, a fixed contact in said housing, a movable contact arm secured at a first of its ends in said housing at a point spaced from said fixed contact and having a free second end positioned adjacent to said fixed contact for cooperation therewith to perform a switching action, said arm having a transverse slot therein intermediate its ends and of stepped width axially of the arm, first and second half cylinders having an outside diameter greater than a smaller width of said slot and smaller than a greater width of said slot and having a kerf in the outer central surface and the side edges of each of the half cylinders, said half cylinders being located in the smaller width portion of said slot with the sides of said portion lying in said edge kerfs and an end of the slot lying in said central kerf of the first of said half cylinders, said arm having an arcuate finger extending generally axially within the wider portion of said stepped slot from the other end thereof with the free end of the finger engaging the central kerf in the second of said half cylinders to resiliently bias said second half cylinder towards said first half cylinder, an actuating rod for said arm extending slidably through said half cylinders and holding them apart against the bias of said finger, temperature responsive means positioned to actuate said rod axially to operate said half cylinders and contact arm with respect to said fixed contact, and stop means positioned to limit the axial movement of said half cylinders by said actuating rod but permitting continued movement of said rod between said half cylinders.

References Cited by the Examiner UNITED STATES PATENTS 2,195,649 4/1940 Hallenbeck et al 2(J0l22 2,314,989 3/1943 Kercher 200-137 FOREIGN PATENTS 732,943 6/ 1955 Great Britain.

ROBERT K. SCI-IAEFER, Acting Primary Examiner. BERNARD A. GILHEANY, Examiner. 

1. THE COMBINATION COMPRISING A BRACKET, A FIXED CONTACT IN SAID BRACKET, A PAIR OF SLIP FRICTION CONNECTED ELEMENTS COMPRISING OF A MOVABLE ARM AND AN ACTUATING ROD, SAID MOVABLE ARM HAVING A FIXED END OPERABLY SECURED TO SAID BRACKET AND HAVING A FREE END MOVABLE WITH RESPECT TO SAID BRACKET, SAID ARM HAVING A TRANSVERSE SLOT THEREIN INTERMEDIATE ITS ENDS, FIRST AND SECOND CHANNEL-SHAPED MEMBERS HAVING A WIDTH GREATER THAN THE WIDTH OF SAID SLOT AND HAVING A WIDTH GREATER THAN THE WIDTH OF SAID OF EACH, SAID MEMBERS BEING LOCATED IN SAID SLOT WITH THE SIDES OF SAID SLOT LYING IN SAID KERFS AND ONE END THEREOF BEARING AGAINST THE FIRST OF SAID MEMBERS, SAID ARM HAVING SPRING MEANS EXTENDING FROM THE OTHER END OF SAID SLOT TO SAID SECOND OF SAID MEMBERS TO RESILIENTLY BIAS SAID SECOND MEMBER TOWARDS SAID FIRST MEMBER, SAID ACTUATING ROD EXTENDING SLIDABLY THROUGH AND FRICTIONALLY ENGAGING SAID MEMBERS AND HOLDING THEM APART AGAINST THE BIAS OF SAID SPRING MEANS SO THAT SAID ROD AND SAID CHANNEL-SHAPED MEMBERS FORM A SLIP FRICTION CONNECTION BETWEEN SAID ARM AND SAID ROD, A MOVABLE CONTACT MOVABLY BY A FIRST OF SAID TWO SLIP FRICTION CONNECTED ELEMENTS AND COOPERABLE WITH SAID FIXED CONTACT TO PERFORM A SWITCHING ACTION, STOP, MEANS POSITIONED TO LIMIT THE MOVEMENT OF SAID FIRST OF SAID ELEMENTS IN A DIRECTION GENERALLY ALONG THE AXIS OF SAID ROD BUT ALLOWING SUFFICIENT MOVEMENT THEREOF TO OPERATE SAID CONTACTS, AND CONDITION RESPONSIVE MEANS OPERABLY CONNECTED TO THE OTHER OF SAID SLIP FRICTION CONNECTED ELEMENTS AND OPERABLE IN RESPONSE TO A CHANGE IN CONDITION TO FIRST MOVE SAID TWO ELEMENTS AND SAID CHANNEL-SHAPED MEMBERS AS A UNIT TO OPERATE SAID CONTACTS AND THE THEREAFTER TO CAUSE SLIDING RELATIVE MOVEMENT BETWEEN SAID ROD AND SAID MEMBERS AFTER THE ENGAGEMENT OF SAID FIRST ELEMENT WITH SAID STOP MEANS SO THAT SAID OTHER ELEMENT MOVES WITH RESPECT TO SAID FIRST ELEMENT. 